L  I  B  R.AFIY 

OF  THE 

UNIVERSITY 

Or    ILLINOIS 

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Publications 
of 

FIELD  MUSEUM  OF  NATURAL 
HISTORY 


GEOLOGICAL  SERIES 
Volume  IV 


CHICAGO,  u.  s.  A. 

1909-1931 


PRINTED  IN  THE  UNITED  STATES  OF  AMERICA 
BY  FIELD  MUSEUM  PRESS 


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>— .  *■  ■ 


CONTENTS 

Pages 

New  Echinoids  from  the  Ripley  Group  of  Mississippi.    By 

Arthur  W.  Slocom i .    .    .  1-16 

New  or  Little  Known  Titanotheres  from  the  Lower  Uintah 

Formations.    By  Elmer  S.  Riggs 17-41 

New  Trilobites  from  the  Maquoketa  Beds  of  Fayette 

County,  Iowa.    By  Arthur  W.  Slocom 41-84 

On  the  Head  of  the  Macropetalichthyids.    By  Erik  A:  son 

Stensio 85-198 

Contributions  to  Paleontology.    By  Sharat  K.  Roy  .    .    .     199-220 

Occurrence  of  the  Alligatoroid  Genus  Allognathosuchus  in 

the  Lower  Oligocene.    By  Bryan  Patterson     ....     221-226 

A  Silurian  Worm  and  Associated  Fauna.    By  Sharat  K. 

Roy  and  Carey  Croneis 227-248 

A  Fossil  Turtle  from  Peru.    By  Karl  P.  Schmidt  ....     249-254 


I  I  30 1 76 


in 


Natural  History  Survey 


r.iHrnrv 


LIST  OF  ILLUSTRATIONS 

PLATES 

I.     Figs.  1-6.    Cassidulus  intermedins  sp.  nov. 
Figs.  7-9.    Cassidulus  hemisphericus  sp.  nov. 

II.     Hemiaster  lacunosus  sp.  nov. 

III.  Linthia  variabilis  sp.  nov. 

IV.  Columnar  Sandstone  of  Lower  Metarhinus  Zone  Ex- 

posed in  the  Canyon  of  White  River. 

V.    Upper  figure.     Green  Clays  Capped  by  Amynodon 
Sandstone. 
Lower  figure.    Fossil-bearing  Sandstone,  Upper  Meta- 
rhinus Zone. 

VI.    Mesatirhinus  superior  sp.  nov. 

VII.    Metarhinus  riparius  sp.  nov. 

VIII.    Metarhinus  earlei  Osborn. 

IX.     Figs.  1,  2.    Dolichorhinus  longiceps. 
Fig.  3.    Metarhinus  cristatus  sp.  nov. 

X.     Dolichorhinus  fluminalis  sp.  nov. 

XL    Fig.  1.    Metarhinus  earlei. 

Figs.  2,  3.     Rhadinorhinus  abbotti. 

XII.     Sthenodectes  incisivum  Douglass. 

XIII.  Isotelus  iowensis  Owen. 

XIV.  Figs.  1-4.    Bumastus  beckeri  sp.  nov. 
Fig.  5.     Megalaspis  beckeri  sp.  nov. 
Figs.  6-8.     Thaleops  ovata  Conrad. 

Figs.  9-15.    Nileus  vigilans  Meek  and  Worthen. 

XV.     Bigs.  1-4.     Sphaerocoryphe  maquoketensis  sp.  nov. 
Figs.  5,  6.     Amphilichas  rhinoceros  sp.  nov. 
Fig.  7.     Amphilichas  clermontensis  sp.  nov. 

XVI.     Figs.  1-4.     Cybeloides  iowensis  sp.  nov. 

Figs.  5-7.     Encrinurus  pernodosus  sp.  nov. 
Figs.  8,  9.     Calymene  fayettensis  sp.  nov. 


XVII. 

XVIII. 

XIX- 
XXVIII. 

XXIX. 

XXX. 

XXXI. 

XXXII. 

XXXIII. 
XXXIV. 

XXXV. 


Figs.  1-3.    Ceraurus  milleranus  Miller  and  Gurley. 

Figs.  4,  5.    Ceraurus  elginensis  sp.  nov. 

Figs.  6-9.    Eccoptochile?  meekanus  S.  A.  Miller. 

Figs.  1-5.  Pterygometopus  fredricki  sp.  nov. 
Figs.  6-8.  Pterygometopus  larrabeei  sp.  nov. 
Fig.  9.     Calymene  gracilis  sp.  nov. 

-XXVII.     Macropetalichthys  rapheidolabis. 

Figs.  1,  2.     Epipetalichthys  wildungensis. 
Figs.  3-5.     Macropetalichthys  rapheidolabis. 

Macropetalichthys  agassizi? 
Epipetalichthys  wildungensis. 

Epipetalichthys  wildungensis. 
Macropetalichthys  rapheidolabis. 

Macropetalichthys  rapheidolabis. 
Epipetalichthys  wildungensis. 

Favosites  limitaris  Rominger. 
Eucalyptocrinus  bordeni  sp.  nov. 


XXXVI. 
XXXVII. 

XXXVIII. 


XXXIX. 


XL. 


Figs.  1,  2. 
Figs.  3,  4. 

Fig.  1. 
Fig.  2. 

Fig.  1. 
Fig.  2. 

Figs.  1-4. 
Figs.  5,  6. 

Figs.  7,  8.    Palaeoneilo  fieldi  sp.  nov. 

Ancyrocrinus  bulbosus  Hall. 

Figs.  1,  2.     Poteriocrinus  robbi  sp.  nov. 
Figs.  3,  4.    Megalomus  canadensis  Hall. 

Figs.  1,  2.    Myalina  sappenfieldi  sp.  nov. 
Fig.  3.     Hyolithes  welleri  sp.  nov. 
Fig.  4.     Wanneria  walcottanus  (Wanner). 
Fig.  5.    Cryptonymus  variolaris  (Brong.). 
Figs.  6,  7.    Niobe?  huberi  sp.  nov. 

Nawnites  gilboensis  gen.  et  sp.  nov. 

Figs.  1-5.    Cryphaeus  australis  Clarke. 
Figs.  6,  7.     Cryphaeus  nicholsi  sp.  nov. 

Figs.  1-5.    Phacopina  devonica  (Ulrich). 
Figs.  6,  8.     Calmonia?  sp. 
Fig.  7.     Platyceras  daviesi  sp.  nov. 
Figs.  9,  10.    Phacops  salteri  Kozlowski. 

Figs.  1-3.    Oracanthus  vetustus  Leidy   (described 

Newberry). 
Figs.  4,  5.    Oracanthus  vetustus  Leidy   (described 

Leidy). 
Fig.  6.    Gyracanthides  murrayi  A.  S.  Woodward. 

Figs.  1-4.     Oracanthus  farringtoni  sp.  nov. 
Fig.  5.    Oracanthus  vetustus  Leidy. 


by 
by 


VI 


XLI.    Left  Mandible  of  Allognathosuchus  riggsi. 

XLII.    Fig.  1.    Sa  =  Shale  Containing  Lecthaylus  gregarius  and 
Associated  Fauna.  Sb  =  Shale  Containing  Only  Mono- 
graptus  vomerinus. 
Fig.  2.    Photograph    Showing    Interstratification    of 
Shale  and  Dolomite. 

XLIII.    Lecthaylus  gregarius  Weller. 

XLIV.    Figs.  1-3.    Lecthaylus  gregarius  Weller. 
Fig.  4.    Protoscolex  ruedemanni  sp.  nov. 
Figs.  5,  6.    Incertae  sedis. 
Fig.  7.     Orbiculoidea  sp. 

XLV.    Fig.  1.    Dictyonema  retiforme  (Hall). 

Fig.  2.     Dictyonema  crassibasale  Gurley. 
Figs.  3,  4,  6,  8.     Desmograptus  micronematodes 

(Spencer). 
Fig.  5.    Dictyonema  teneUum  Spencer. 
Fig.  7.     Palaeodictyota  bella  (Hall  and  Whitfield). 
Figs.  9-14.    Monograptus  vomerinus  (Nicholson). 

XLVI.    Plastral  Aspect  of  Podocnemis  olssoni  sp.  nov. 

XLVII.     Carapacial  Aspect  of  Podocnemis  olssoni  sp.  nov. 


No.  1 

Fig.    1. 
Fig.    2. 

No.  2 

Fig.    1. 
Fig.    2. 

No.  3 

Fig.    1. 

No.  4 

Fig.  1. 

Fig.  2. 

Fig.  3. 

Fig.  4. 

Fig.  5. 

Fig.  6. 

Fig.  7. 

Fig.  8. 

Fig.  9. 


TEXT  FIGURES 

Page 

Diagram  of  Linthia  variabilis 2 

Diagram  of  the  Floscelle  of  Cassidulus  intermedins  .  3 

Section  of  Metarhinus  Beds,  as  Exposed  in  the  North 

Wall  of  White  River 20 

Panoramic   Section   of  the  Amynodon  Beds,  from 

Kennedy's  Basin  to  White  River  Canyon  ....  21 

Diagrammatic  Figure  of  a  Trilobite 44 

Macropetalichthys  rapheidolabis 94 

Macropetalichthys  rapheidolabis 97 

Macropetalichthys  rapheidolabis 101 

Macropetalichthys  rapheidolabis 104 

Macropetalichthys  rapheidolabis 110 

Macropetalichthys  rapheidolabis Ill 

Macropetalichthys  rapheidolabis 117 

Macropetalichthys  rapheidolabis 128 

Macropetalichthys  rapheidolabis 133 

vii 


Fig.  10.    Macropetalichthys  rapheidolabis 136 

Fig.  11.    Macropetalichthys  rapheidolabis 139 

Fig.  12.    Macropetalichthys  rapheidolabis 141 

Fig.  13.     Macropetalichthys  rapheidolabis 142 

Fig.  14.     Titanichthys  agassizi  Newb 143 

Fig.  15.     Macropetalichthys  rapheidolabis 144 

Fig.  16.    Macropetalichthys  agassizi? 151 

Fig.  17.    Epipetalichthys  wildungensis  Jaekel 154 

Fig.  18.    Epipetalichthys  wildungensis 155 

Fig.  19.    Epipetalichthys  wildungensis 158 

Fig.  20.    Phlyctenaspis  acadica 165 

Fig.  21.     Phlyctenaspis  acadica 166 

Fig.  22.    Sketch  of  a  Sensory  Canal  Groove  of  a  Phlyctenaspid 

in  Transversal  Section.    Magnified 168 

Fig.  23.     Restoration  of  the  Outlines  of  the  Primordial  Neuro- 

cranium.    A,  of  Coccosteus;  B,  of  Dinichthys  .    .    .  171 

Fig.  24a.     Dermal  cranial  roof  of  Coccosteus  decipiens  ....  174 

Fig.  24b.     Dermal  cranial  roof  of  Dinichthys  halmodeus    .    .    .  175 

Fig.  25.    Coccosteus  decipiens 178 

Fig.  26.    Jagorina  pandora  Jaekel 183 


V1U 


Field  Museum  of  Natural  History. 
Publication  134. 
Geological  Series.  Vol.  IV,  No.   1 


NEW  ECHINOIDS  FROM  THE 
RIPLEY  GROUP  OF  MISSISSIPPI 


By 

Arthur  Ware  Slocom, 

Assistant  Curator,  Section  of  Invertebrate  Paleontology. 


Oliver  Cummings  Farrington, 
Curator,  Department  of  Geology. 


Chicago,  U.  S.  A. 

May    15,    1909. 


NEW  ECHINOIDS  FROM  THE  RIPLEY  GROUP  OF  MISSISSIPPI. 


BY   ARTHUR  WARE  SLOCOM 


The  specimens  upon  which  this  paper  is  based  were  collected  by 
the  writer  in  the  spring  of  1908,  during  a  trip  made  to  Mississippi  for 
the  purpose  of  obtaining  a  representative  series  of  fossils  from  the 
well-known  Cretaceous  and  Tertiary  deposits  of  that  state. 

The  Ripley  formation  of  Mississippi,  from  which  the  specimens 
here  described  were  obtained,  extends  southward  from  Tennessee,  on 
the  border  of  which  state  it  has  a  width  of  about  10  miles.  In  the 
southern  part  of  Tippah  County  it  widens  out  to  about  1 5  miles  and 
from  thence  gradually  narrows  as  it  passes  south  through  Union 
and  Pontotoc  Counties  until  near  Houston  in  Chickasaw  County  it 
disappears  altogether.  For  the  most  part  this  formation  occupies 
the  highlands  and  is  locally  known  as  the  Pontotoc  Ridge.  Over  a 
large  part  of  this  region  the  Ripley  is  overlain  by  red  sands  and  clay 
of  the  Lafayette  and  Wilcox  groups,  so  that  the  Ripley  beds  are  often 
found  in  the  gullies  and  along  the  streams  and  are  recognized  on 
account  of  their  light  color.     They  are  locally  called  "white  gullies." 

At  Pontotoc,  Mississippi,  three  localities  were  visited,  viz:  (1) 
the  Patterson  farm  about  three  miles  southeast  of  town;  (2)  the 
bluffs  on  either  side  of  One  Mile  Run,  about  a  mile  south  of  town  on 
the  Houston  road;  and  (3)  the  roadside  near  the  southern  edge  of  the 
village.  These  two  latter  outcrops  are  similar  in  position,  compara- 
tively near  together  and  will  be  considered  in  this  paper  as  one  locality. 
The  outcrop  on  the  Patterson  farm  lies  somewhat  higher  than  the 
other  two  and  is  probably  higher  geologically.  At  all  these  localities 
well  preserved  echinoids  were  found.  About  200  specimens  were 
collected  which  proved,  on  examination,  to  represent  six  species, 
four  of  which  are  new  and  are  here  described. 


CLASSIFICATION   AND  TERMINOLOGY. 

The  classification  here  used  is  that  prepared  by  P.  M.  Duncan,* 
and  given  in  the  English  edition  of  Zittel's  Text  Book  of  Paleontology. 

*  P.   M.   Duncan   1889,  Revision  of  the  Genera  and  Great  Groups  of  the 
Echinoidea,  Jour.  Linnean  Soc.  Vol.  XXIII. 

Field  Mus.  Nat.  Hist.  Geol.  Ser.  Vol.  IV,  No.   1. 


2     Field  Museum  of  Natural  History  —  Geology,  Vol.  IV. 

The  terminology  of  Desor*  with  some  modifications  is  adhered  to. 
It  may  be  briefly  stated  as  follows : 

Echinoids  or  Sea  Urchins:  Marine  animals  without  arms  or  stem, 
the  bodies  encased  in  a  solid  or  slightly  flexible  test  or  shell,  varying 
in  shape  from  spherical  to  flat ;  composed  of  numerous  closely  placed 
plates,  covered  with  spines.  The  mouth  is  on  the  ventral  or  actinal 
surface;  the  anus  either  in  the  apical  system  or  somewhere  in  the 
posterior  interambulacral  area.  The  plates  of  the  ambulacral  areas 
are  more  or  less  extensively  perforated  for  the  protrusion  of  the  am- 
bulacra or  tube  feet. 

Dorsal  Surface:  (Af)  The  upper,  usually  convex  surface,  on 
which  are  situated  the  apical  system,  petals,  etc. 

Ventral  or  Actinal  Surface:  (C)  The  lower  surface  on  which  the 
peristome  is  situated. 

Anterior  Sulcus:  (as)  A  more  or  less  distinct  groove  in  the  an- 
terior margin  of  the  test.  In  it  is  situated  the  anterior  ambulacral 
area. 


iamb 


iamb 


Fig.  i.     Diagram  of  Linthia  variabtlis.    A,  dorsal  view.     B,  posterior  view.    C,  ventral  view. 


Ambulacral  (amb.)  and  Interambulacral  Areas:  (iamb.)  The  test 
of  practically  all  echinoids  is  divided  into  ten  segments  or  areas, 
five  ambulacral  and  five  interambulcral  areas.  In  living  echinoids 
and  most  Mesozoic  or  Cenozoic  fossil  echinoids,  including  all  species 
mentioned  in  this  paper,  each  area  consists  of  two  rows  of  plates. 

Poriferous  Zones:  On  each  side  of  the  ambulacral  areas  are  bands 
or  zones  containing  openings  or  pores  through  which  issue  the  tentacles 
or  tube  feet.  There  are  ten  poriferous  zones,  two  to  each  ambulacral 
area.  In  some  echinoids  there  is  quite  a  space  between  the  poriferous 
zones  and  this  space  is  called  the  inter  poriferous  zone. 

Simple  Ambulacra:  Those  in  which  the  pores  of  the  poriferous 
zones  have  the  same  disposition  from  the  apex  to  the  peristome. 
This  is  the  case  in  all  "regular  echinoids." 

*  E.  Desor  1858.     Synopsis  des  Echinides  Fossiles  Paris, 
t  The  letters  in  parentheses  refer  to  those  of  Figs.  1  and  2. 


May,  1909. 


New  Echinoids  —  Slocom. 


Petaloid  Ambulacra:  In  some  genera  the  ambulacral  areas  are  wide 
near  the  apex  and  the  poriferous  zones  are  bounded  by  a  groove.  The 
part  of  the  area  having  this  form  is  called  the  petal  (p).  In  other 
genera  the  poriferous  zones  are  similar  in  form  to  the  above,  but  the 
petals  are  not  closed  at  their  distal  ends  and  the  zones  continue.  The 
disposition  of  the  pores  is,  however,  radically  changed.  Areas  having 
this  form  are  called   subpetaloid. 

Apical  System  (a) :  A  disc  ordinarily  composed  of  ten  plates,  (PI.  II 
fig.  5)  five  of  which  called  genital  plates  form  the  summits  of  the  inter- 
ambulacral  areas  and  five  called  radial  plates,  by  some  authors  oculars, 
form  the  summits  of  the  ambulacral  areas.  Two  or  more  of  the 
genital  plates  may  be  fused,  thus  reducing  the  number.  One  of  the 
genital  plates  is  usually  larger  than  the  others  and  bears  a  spongy 
protuberance  filled  with  minute  pores  called  the  madreporite. 


b    *~    pk 

Fig.  2.     Diagram  of  the  floscelle  of  Cassidulus  intermedins. 

Floscelle:  (Fig.  2)  In  the  family  Cassidulidae  the  ambulacral  areas 
assume  a  peculiar  flowerlike  form  around  the  peristome,  called  the 
floscelle.  The  floscelle  is  composed  of  five  enlargements  of  the  pori- 
ferous zones  called  the  phyllodes  (ph).  These  five  phyllodes  are 
separated  from  each  other  by  five  inflated  plates  of  the  interambulacral 
areas  about  the  peristomal  margin.  These  inflated  plates  are  called 
bourrelets  (b). 

Fascioles:  Narrow  bands  apparently  smooth  but  in  reality  formed 
of  microscopic  tubercles,  which  during  life  bear  vibrating  cilia.  They 
have  been  divided  into:  (1)  the  peripetalous  fasciole  (pf)  which  sur- 
rounds the  petals;  (2)  the  marginal  fasciole  which  follows  the  sides; 
(3)  the  subanal  fasciole  which  is  limited  to  the  posterior  face;  and  (4) 


4     Field  Museum  of  Natural  History  —  Geology,  Vol.  IV. 

the  lateral  fasciole  (If)  which  branches  from  the  peripetalous  fasciole 
and  passes  beneath  the  periproct. 

Tubercles:  (PL  II  figs.  8,9.)  Wart-like  protuberances  which  occur  on 
the  plates  of  most  echinoids.  They  vary  in  size  from  quite  large  to 
microscopic  granulations.  Tubercles  consist  of  two  parts,  the  boss 
and  the  mamelon.  The  base  or  boss  may  be  either  plain  or  crenulated. 
The  mamelon  is  a  small  rounded  protuberance  above  the  boss  to  which 
in  life,  a  spine  is  attached.  A  plain  or  sunken  space  surrounding  the 
boss  generally  marked  by  a  ring  of  granules  is  called  the  areole  or 
scrobicule. 

Periproct  (pt) :  The  upper  or  posterior  opening  in  the  shell,  im- 
properly called  the  anus,  but  which  contains  the  latter.  The  periproct 
is  closed  by  a  membrane  to  which  the  anal  plates  are  attached.  These 
plates  may  be  few  and  symmetrical,  or  numerous  and  irregular,  and 
arranged  concentrically  about  the  anal  opening.  The  position  of 
the  periproct  is  within  the  apical  system  in  "regular  echinoids"  but 
in  "irregular  echinoids"  it  is  situated  somewhere  in  the  posterior 
interambulacral  area.  It  may  be  either  on  the  dorsal  or  ventral 
surface.  The  position  of  the  periproct  is  of  great  systematic  impor- 
tance. 

Peristome  (ps) :  The  lower  opening  of  the  shell ;  it  is  situated  on 
the  ventral  surface,  either  at  the  center  or  on  the  median  line  between 
the  center  and  the  anterior  margin.  In  form  it  may  be  decagonal, 
pentagonal,  oval,  bilabiate,  etc.  It  contains  the  buccal  membrane 
in  the  center  of  which  the  mouth  is  situated. 

Labrum:   (1)    The  posterior  lip  of  the  peristome. 

Proximal:  Nearest  to  the  apex. 

Distal:  Farthest  from  the  apex. 

Lateral:    Pertaining  to  the  side. 


May,  1909.  New  Echinoids  —  Slocom.  5 

DESCRIPTION  OF  GENERA  AND  SPECIES. 

Order  SPATANGOIDA. 

Family  CASSIDULIDiE. 

Genus  CASSIDULUS  Lamarck  1801. 

Test  small,  oblong,  depressed,  broadest  posteriorly,  longer  than 
broad,  broader  than  high,  convex  dorsally,  flat  or  concave  ven- 
trally. 

Apical  system  eccentric  in  front  or  subcentral;  four  perforated 
genital  plates;  the  madreporite  passing  back  and  separating  the 
postero-lateral  genitals  but  not  the  radial  plates.  Ambulacral  areas 
subsimilar,  short,  flush,  subpetaloid,  not  closing;  pores  continued 
from  the  petaloid  part  to  the  floscelle,  which  is  well  developed.  Ten- 
tacles both  simple  and  branchial  (heteropodous) .  Peristome  eccentric 
in  front,  the  bourrelets  narrow  and  strong,  the  phyllodes  in  grooves, 
One  peristomal  plate  to  each  interradium.  Usually  a  median  band 
behind  the  peristome  where  there  are  no  tubercles  and  where  the  test 
is  either  cribriform,  pitted  or  plain,  or  it  may  be  absent.  Periproct 
supramarginal,  in  a  depression  or  at  the  commencement  of  a  groove, 
elongated  longitudinally.  Tubercles  small  and  very  close  together 
on  the  dorsal  surface,  large  and  separated  on  the  ventral,  except  on 
the  longitudinal  median  area. 

Range  Cretaceous  and  Eocene. 

Cassidulus    Subquadratus  Conrad. 

i860.  C.  subquadratus     Conrad,  Jour.  Acad.  Nat.  Sci.  Phil.,  2nd  ser. 

Vol.  4,  p.  291,  pi.  47,  fig.  19. 
1 89 1  C.  subquadratus      Clark,  Johns  Hopkins  Univ.  Circ.  No.  87, 

p.  76. 
1893  C-  subquadratus     Clark,  Bull.  U.  S.  G.  S.  No.  97,  p.  70,  pi. 

31,  fig.  1  a-h. 
Original  description:     " Suborbicular,  flat  beneath,  flexuous  pos- 
teriorly;  lateral  and  end  slopes  truncated;  anus  very  large,  obtusely 
ovate,  with  a  depression  beneath,  extending  to  the  margin,  which  at 
that  point  is  salient;  ambulacra  lanceolate. 

Length  3^  inches;  Diameter  2%  inches;   Height  1%  inches. 
Locality.     Tippah    county,     Mississippi."     Clark    gives    Holly 
Springs  as  the  locality  of  this  species. 


6     Field  Museum  of  Natural  History  —  Geology,  Vol.  IV. 

No  entire  specimens  of  this  species  were  collected  by  the  writer, 
but  six  fragments,  Cat.  No.  P  10345,  of  sufficient  size  for  identification 
were  found  on  the  Patterson  farm  near  Pontotoc,  Mississippi. 

Cassidulus    intermedius  sp.  nov.  Plate  I,  Figs.  1-6. 

'  Test  oval,  greatest  width  posterior  to  the  center;  rounded  anter- 
iorly, slightly  rostrated  posteriorly;  dorsal  surface  convex,  apex 
eccentric  anteriorly  and  inflated,  sides  declining  about  equally  towards 
the  margins  which  are  slightly  inflated;  the  peristomal  concavity 
occupying  more  than  half  of  the  ventral  surface.  Ambulacral  areas 
narrow  and  flush,  poriferous  zones  subpetaloid  on  the  upper  part  of 
the  dorsal  surface  to  a  point  varying  in  the  different  areas  from  about 
one  third  to  nearly  one  half  the  distance  from  the  margin  to  the  apical 
system ;  the  zones  are  then  contracted  and  continue  as  narrow  bands 
over  the  margin  to  the  vicinity  of  the  peristome,  where  they  abruptly 
widen,  and  again  narrow  to  the  peristome  forming  a  floscelle.  The 
pores  are  distant  and  paired  on  the  petaloid  portion  and  in  the  flos- 
celle; on  the  narrow  connecting  portions  they  are  single,  small  and 
indistinct.  In  the  petaloid  areas  the  pores  of  the  outer  rows  are  slit- 
like, those  of  the  inner  rows  round  and  smaller ;  each  pair  is  connected 
by  a  groove.  Interambulacral  areas  composed  of  large  plates,  the 
plates  nearest  the  peristome  in  each  area  inflated  forming  the  bour- 
relets.  Dorsal  surface  covered  with  small  crowded  tubercles  with 
slightly  sunken  areoles,  the  tubercles  on  the  ventral  surface  rapidly 
increasing  in  size  and  distance  apart  as  they  approach  the  peristome. 
A  wide,  longitudinal  median  band  extends  from  near  the  anterior 
margin  through  the  floscelle  to  the  posterior  margin.  This  band  is 
without  tubercles  and  the  surface  is  smooth  except  where  it  passes 
through  the  floscelle.  The  apical  system  in  the  type  specimen  is  too 
incomplete  for  detailed  description,  but  appears  similar  to  other  species 
of  this  genus.  The  peristome  is  situated  slightly  in  front  of  the  center 
of  the  ventral  surface,  pentagonal,  surrounded  by  a  well-marked 
floscelle,  the  bourrelets  large  and  prominent,  the  phyllodes  very 
narrow  as  they  reach  the  peristome  and  situated  in  grooves.  The 
periproct  is  elongated  longitudinally  and  situated  on  the  dorsal  sur- 
face at  about  one  third  the  distance  from  the  posterior  margin  to  the 
apex  in  a  deep  groove.  The  dimensions  of  the  type  specimen  are: 
Length  25.6  mm.,  width  22.7  mm.,  height  9.6  mm. 

This  description  is  based  on  a  single  specimen,  Cat.  No.  P  10346, 
collected  by  the  writer.  The  specimen  had  been  slightly  crushed  on 
the  left  side,  a  few  of  the  plates  of  the  left  interambulacral  area  and 
part  of  the  apical  system  are  missing,  but  the  general  form  and  all 


May,  1909.  New  Echinoids  —  Slocom.  7 

other  parts  of  the  test  are  complete.  In  general  form  this  species 
resembles  C.  cequoreus,  but  it  is  not  so  high  in  proportion  to  its  length, 
the  periproct  is  somewhat  higher,  the  pores  in  the  outer  rows 
of  the  petaloid  portions  are  slitlike  instead  of  round  and  the 
expansions  of  the  phyllodes  are  wider.  C.  intermedins  resembles 
C.  micrococcus  in  the  slitlike  pores  of  the  outer  rows  of  the  petaloid 
areas  and  in  the  expansion  of  the  phyllodes,  but  the  position  of  the 
pores  in  these  expansions  is  more  like  those  of  C.  cequoreus.  The 
position  of  the  periproct  is  midway  between  that  of  C.  micrococcus 
and  C.  cequoreus,  the  size  and  shape  of  the  test  is  quite  unlike  C. 
micrococcus  and  the  extension  of  the  longitudinal  median  band  in 
front  of  the  peristome  on  the  ventral  surface  does  not  appear,  from 
the  description  and  figures,  to  occur  in  either  of  the  other  species. 
The  name  adopted  for  this  species  refers  to  the  characters  inter- 
mediate between  C.  cequoreus  and  C.  micrococcus  which  the  species 
exhibits. 

Locality:  Ripley  Group  near  the  southern  edge  of  the  village  of 
Pontotoc,  Mississippi. 

Cassidulus  hemisphericus  sp.  nov.  Plate  I,  Figs.  7-9. 

Test  subhemispherical  with  its  transverse  diameter  somewhat 
shorter  than  the  longitudinal,  sides  arcuate,  margins  angular,  ventral 
surface  flat  or  nearly  so.  Ambulacral  areas  wide,  subpetaloid  on  the 
top  of  the  dorsal  surface,  not  closed  distally,  petals  subequal  in 
length,  extending  about  half  way  from  the  apex  to  the  margin, 
slightly  convex;  from  the  distal  end  of  the  petals  the  ambulacral 
areas  are  continued  as  a  band  which  gradually  increases  in  width 
from  the  petal  to  the  margin,  most  of  the  way  being  wider  than  the 
petal.  On  the  ventral  surface  the  bands  slightly  narrow  to  the 
floscelle.  The  floscelle  is  not  well  preserved  in  the  type  specimen,  but 
enough  is  preserved  to  determine  that  the  bourrelets  are  prominent 
and  that  the  phyllodes  are  in  grooves.  The  apical  system  is  central 
but  the  form  of  the  various  plates  of  which  it  is  composed  cannot  be 
determined.  The  interambulacral  areas  are  about  equal  in  size. 
They  form  an  acute  angle  near  the  apex  and  rapidly  expand  to  the 
margin,  the  plates  being  comparatively  large.  All  the  plates  of  the 
dorsal  surface,  with  the  exception  of  those  of  the  petals,  are  marked 
by  prominent  lines  subparallel  to  the  edge  of  the  plates.  These  lines 
are  farther  apart  on  the  lateral  edges  than  on  the  proximal  and  distal 
edges.  They  appear  to  be  lines  of  growth.  The  middle  portion  of 
the  plates  within  this  series  of  lines  is  inflated,  so  that  in  the  small 
plates  of  the  interambulacral  areas,  near  the  apex,  the  centers  of 


8      Field  Museum  of  Natural  History — Geology,  Vol.  IV. 

the  plates  appear  as  prominent  nodes.  These  middle  portions  of  the 
plates  are  free  from  tubercles,  but  the  parts  of  the  plates  covered  by 
the  parallel  lines  and  the  plates  of  the  petals  are  covered  with  minute 
tubercles  closely  crowded  together.  The  lines  are  much  less  prom- 
inent on  the  plates  of  the  ventral  surface  and  the  tubercles  are  larger, 
with  slightly  sunken  areoles  and  more  evenly  distributed  over  the 
surface  except  on  the  longitudinal  median  band,  which  extends  from 
the  peristome  to  the  posterior  margin.  The  peristome  is  situated  at 
the  center  of  the  ventral  surface,  surrounded  by  a  floscelle,  the  bourre- 
lets  are  prominent  and  the  phyllodes  are  depressed  and  contracted 
into  narrow  grooves,  where  they  reach  the  peristome.  The  periproct 
is  supramarginal,  but  its  form  and  exact  position  are  unknown  because 
that  portion  of  the  posterior  interambulacral  area  near  the  margin 
is  missing.  The  measurements  of  the  type  specimen,  Cat.  No.  P 
10347,  are:  Length  34.7  mm.  width  26:7  mm.,  height  19.5  mm. 
Allowing  for  the  lateral  crushing  it  is  probable  that  the  length  and 
width  were  originally  about  32  mm.  and  29  mm.  respectively. 

It  is  to  be  regretted  that  other  and  more  perfect  specimens 
of  this  species  could  not  have  been  found  and  the  writer  has  endeav- 
ored to  obtain  such  specimens  by  correspondence,  but  so  far  without 
success.  The  specimen  on  which  the  description  is  based  is  crushed 
laterally,  and  in  three  of  the  interambulacral  areas  and  the  region 
about  the  peristome  there  are  some  plates  missing.  Three  of  the 
ambulacral  and  two  of  the  interambulacral  areas  are  practically 
complete.  The  entire  petaloid  portion  of  the  dorsal  surface  is  in  good 
condition,  so  that  the  only  important  character  that  is  in  doubt  is  the 
exact  form  and  position  of  the  periproct.  The  five  pairs  of  plates 
above  the  margin  in  the  posterior  interambulacral  area  are  missing 
and  the  periproct  was  situated  somewhere  within  this  space.  The 
specific  name  is  adopted  on  account  of  the  hemispherical  form  of 
the  test,  which  distinguishes  it  to  a  marked  degree  from  any  other 
species  of  the  genus. 

Locality :  The  type  specimen  was  collected  by  the  writer  in  the 
"white  gullies"  of  the  Ripley  Group  on  the  Patterson  farm,  about 
three  miles  south  of  Pontotoc,  Mississippi. 


May,  1909.  New  Echinoids  —  Slocom.  9 

Family  SPATANGID^). 
Genus  HEMIASTER  Desor  1847. 

Urchins  with  a  short,  elevated,  oval  or  cordiform  test.  Apical 
system  in  general  excentral  and  posterior.  Ambulacral  areas  peta- 
loid,  unequal  in  length,  and  lodged  in  depressions  of  the  dorsal  surface; 
poriferous  zones  large  and  equal  in  the  same  ambulacral  area,  pores 
elongated  and  placed  close  together.  Anterior  area  lodged  in  a  long 
shallow  sulcus;  poriferous  zones  very  narrow  and  composed  of  small 
round  pores  sparsely  disposed  in  oblique,  widely  separate,  simple 
pairs.  Fasciole  single,  peripetalous,  and  circumscribing  the  ambul- 
acral areas.  Apical  disc  small  and  compact,  four  perforated  genital 
plates,  and  five  very  small  radial  plates.  Peristome  bilabiate, 
very  excentral,  opening  at  the  anterior  fourth  part  of  the  base.  Peri- 
proct  opening  high  up  on  the  posterior  border,  which  is  in  general 
flat,  and  obliquely  truncated. 

Hemiaster  differs  from  Micraster  in  having  a  single  peripetalous 
fasciole  and  no  anal  fasciole;  the  test  is  likewise  in  general  shorter, 
more  inflated,  and  the  posterior  pair  of  ambulacral  areas  are  much 
shorter  than  the  anterior  pair.  Hemiaster  differs  from  Linthia  in 
having  only  a  peripetalous  fasciole,  the  latter  having  both  peripetalous 
and  lateral  fascioles. 

Range  Cretaceous  to  Recent. 

Hemiaster  parastatus  (Morton). 

1830.  Spatangus  sp.     Mort.,  Am.  Jour.  Sci.,  1st  ser.,  Vol.  17,  p.  286. 
1830.  S.  cor-marinum     (?)  Mort.,  Am.  Jour.  Sci.,  1st  ser.,  Vol.  18, 

p.  250,  pi.  3,  fig.  10. 
1830.  5.  cor-marinum     (?)  Mort.,  Jour,  Acad.  Nat.  Sci.  Phil.,  1st 

ser.,  Vol.  6,  p.  199. 

1833.  S.  parastatus     Mort.,  Am.  Jour.  Sci.,  1st  ser.,  Vol.  23,  p.  294. 

1834.  5.  parastatus     Mort,.  Synop.  Org.  Rem.  Cret.  Gr.  U.  S.,  p.  77, 
pi.  3,  fig.  21. 

1853.  Hemiaster  parastatus     Marcou,  Explan.  Text  to  Geol.  Map. 

U.  S.,  and  Brit.  Prov.  N.  A.,  p.  47,  pi.  7,  fig.  8. 
1855.  H.  parastatus   d'Orb.,  Pal.  France,  Terr.  Cret.,  Vol.  6,  p.  265, 

pi.  894,  fig.  4. 
1864.  H.  (?)  parastatus     Meek,  Check  List  Inv.  Foss.  N.  A.,  Cret. 

and  Jur.,  p.  3. 
1891.  H.  parastatus     Clark,  Johns  Hopkins  Univ.  Circ,  Vol.  10, 

No.  87,  p.  77. 


io    Field    Museum  of  Natural  History  —  Geology,  Vol.  IV. 

1893.  H.  parastatus     Clark,  Johns  Hopkins  Univ.  Circ,  Vol.  12, 

No.  103,  p.  52. 
1893.  H.  parastatus     Clark,  Bull.  U.  S.  G.  S.,  No.  97,  p,  83,  pi.  45, 

figs.  1  a-m. 
1905.  H.  parastatus     Johns.,  Proc.  Acad.  Nat.  Sci.  Phil.,   1905, 

p.  7. 
1907.  H.  parastatus     Weller,  Paleontology  of  New  Jersey,  Vol.  4, 

p.  298,  pi.  15,  figs.  1-13. 
This  species  was  described  from  the  Upper  Cretaceous  limestone 
of  Timber  Creek,  New  Jersey,  and  has  been  reported  from  the  Ripley 
Group  of  Alabama. 

Five  specimens  of  this  species,  Cat.  No.  P  10341,  were  collected 
by  the  writer  near  the  southern  edge  of  the  village  of  Pontotoc, 
Mississippi,  in  the  so-called  "white  gullies"  of  the  Ripley  Group. 

Hemiaster  lacunosus  sp.  nov.  Plate  II,  Figs.  1-7. 

Test  small,  indistinctly  cordate,  ventral  surface  moderately  con- 
vex, dorsal  surface  convex,  strongly  elevated  in  the  posterior  inter- 
ambulacral  area  and  gradually  sloping  with  an  indistinct  anterior 
sulcus;  anterior  and  lateral  borders  inflated,  posterior  margin  trun- 
cated. Ambulacral  areas  petaloid,  with  straight  petals  situated  in 
depressions  of  the  surface,  the  antero-lateral  pair  nearly  twice  as 
long  as  the  postero-lateral  pair;  poriferous  zones  of  the  paired 
petals  wide,  pores  transversely  elongate  and  situated  far  apart. 
Anterior  petal  longer  but  narrower  than  the  others  and  situated  in  a 
deep  depression  which  grades  into  an  indistinct  anterior  sulcus; 
poriferous  zones  of  this  petal  narrow  and  far  apart;  pores  small, 
round  and  separated  by  a  tubercle.  Interambulacral  areas  broad 
and  composed  of  large  plates.  Surface  of  the  test  covered  with  a 
multitude  of  small  tubercles  with  sunken  areoles  that  increase  in 
size  toward  the  peristome.  The  tubercles  have  perforated  mamelons 
and  crenulated  bosses,  the  inter-spaces  being  filled  with  microscopic 
granulations.  Peripetalous  fasciole  wide  and  distinct,  moderately 
bent  inward  between  the  petaloid  areas  except  the  two  posterior 
ones.  Apical  disc  sunken,  small  and  situated  somewhat  posterior 
to  the  center  of  the  dorsal  surface,  the  four  genital  plates  distinctly 
perforated  and  separated  by  five  small  radial  plates.  Right  anter- 
ior genital  plate  large,  convex  and  forming  the  madreporite. 
Peristome  transversely  arched,  bilabiate,  with  prominent  labrum. 
Periproct  about  the  size  of  the  peristome,  elongated  vertically 
and  situated  near  the  top  of  the  posterior  truncation. 


May,  1909. 


New  Echinoids  —  Slocom. 


11 


The  dimensions  of  a  number  of  practical^  perfect  specimens  are 
as  follows: 


Cat.  Xo. 
P  10342 

Length 

Width 

Height 

mm 

mm 

mm 

A 

23-4 

23.6 

15  3 

B 

23-3 

21.7 

i7- 

C 

22.5 

21 . 1 

16.5 

D 

20.5 

20 . 

151 

E 

17.8 

16.3 

11. 8 

H.  lacunosus  resembles  H.  parastatus  in  general  form  and  pro- 
portions, but  is  distinguished  from  that  species  by  its  smaller  size 
and  by  the  sunken  areoles  of  the  tubercles.  Moreover,  the  posterior 
interambulacral  area  is  rounded,  while  in  H.  parastatus  it  is  in  the 
form  of  a  ridge.  H.  lacunosus  is  similar  to  H.  Stella  in  size,  but  differs 
from  it  in  the  shape  of  the  fasciole,  the  sunken  areoles  and  the  form 
of  the  anterior  margin.  It  resembles  H.  dalli  in  having  sunken  areoles, 
but  in  general  form  these  two  species  are  quite  dissimilar.  The 
specific  name  adopted  refers  to  the  sunken  areoles  by  which  the  species 
is  distinguished. 

Locality:  This  species  is  abundant  at  all  three  of  the  outcrops 
visited  at  Pontotoc  and  about  150  specimens  were  collected.  The 
test  is  very  thin  and  and  fragile,  so  that  of  the  150  specimens  less 
than  a  dozen  were  unbroken.  Three  specimens  which  undoubtedly 
belong  to  this  species  were  also  collected  by  the  writer  at  Houston, 
Mississippi,  associated  with  fossils  of  the  Selma  Chalk,  but  as  the  Rip- 
ley and  Selma  formations  are  both  reported  from  Houston  and  the 
fossils  were  found  at  the  bottom  of  gullies  of  some  size,  it  is  quite 
probable  that  the  echinoids  were  of  Ripley  age.  , 


Genus  LINTHIA  Merian  1853. 

Test  variable  in  size,  oval  or  cordiform,  grooved  anteriorly, 
subacuminate  or  truncated  posteriorly,  tumid  and  gibbous  dorsally, 
almost  flat  ventrally.  Apical  system  small,  eccentric  anteriorly, 
composed  of  four  perforated  genital  plates,  one  of  which  forms  the 
madreporite,  and  five  small  radial  plates.  Ambulacral  areas  diverse; 
anterior  one  in  a  broad  groove,  pores  round  and  small.  Antero- 
lateral pair  with  petaloid  parts  in  grooves,  moderately  long,  diver- 
gent, nearly  closing  distally;  pairs  of  pores  equal  or  subequal.  Pos- 
tero-lateral  pair  also  in  sunken  grooves,   less  divergent  and  shorter 


12    Field  Museum  of  Natural  History  —  Geology,  Vol.  IV. 

than  the  others.  Ambulacra  form  the  greater  part  of  the  peristomal 
margins,  and  are  moderately  broad  on  either  side  of  the  sternum. 
Peristome  eccentric  in  front,  semilunar,  with  a  well-developed  pos- 
terior labrum.  Periproct  at  the  upper  part  of  the  posterior  truncation. 
A  peripetalous  fasciole,  and  a  lateral  fasciole  starts  from  the  peri- 
petalous  fasciole  close  to  the  antero-lateral  petals  and  passes  beneath 
the  periproct.  Tubercles  crowded,  increasing  in  size  as  they  approach 
the  peristome,  usually  crenulate  and  perforate,  and  either  on  flat  or 
in  sunken  areoles. 

Range  Cretaceous  to  Recent. 

Linthia  variabilis  sp.  nov.  Plate  III,  Figs.  i-ii. 

Test  distinctly  cordate,  truncated  posteriorly,  ventral  surface 
depressed  convex,  dorsal  surface  elevated,  forming  a  sharp  ridge  in 
the  posterior  interambulacral  area.  Sides  inflated  and  sloping  to  the 
lateral  and  anterior  margins;  posterior  truncation  slightly  concave 
and  the  angle  between  the  truncation  and  the  base  line  varying  from 
77°  to  900.  Ambulacral  areas  straight,  petaloid,  situated  in  compara- 
tively deep  depressions  of  the  dorsal  surface.  Antero-lateral  pair 
about  one  and  one-half  times  the  length  of  the  postero-lateral  pair, 
poriferous  zones  of  these  four  petals  wide,  pores  elongated  and  slit- 
like. Each  pair  of  pores  connected  by  a  shallow  groove  and  the  pore 
near  the  border  of  the  petal  the  larger.  Unpaired  anterior  ambulacral 
area  situated  in  a  deep  depression  the  continuance  of  which  forms  a 
sulcus  in  the  anterior  margin.  Poriferous  zones  of  this  area  narrow 
and  situated  far  apart.  Pores  round  and  each  pair  separated  by  a 
tubercle.  Interambulacral  areas  broad  and  composed  of  large  plates. 
Surface  of  the  test  covered  with  minute  perforated  tubercles  having 
crenulated  bosses.  These  tubercles  increase  in  size  as  they  approach 
the  peristome.  Interspaces  filled  with  small  tubercles  and  microscopic 
granulations.  Both  peripetalous  and  lateral  fascioles  are  clearly 
defined,  peripetalous  fasciole  decidedly  bent  inward  between  the 
antero-lateral  and  postero-lateral  petals  and  somewhat  less  so  between 
the  other  petals.  Apical  system  situated  in  the  center  or  somewhat 
anterior  to  the  center  of  the  dorsal  surface;  small,  depressed,  having 
the  four  genital  plates  perforated  and  separated  by  five  small  radials. 
Peristome  transversely  elliptical,  situated  near  the  anterior  margin. 
Labrum  prominent.  Periproct  somewhat  elongated  vertically  and 
situated  near  the  top  of  the  posterior  truncation. 


May,  1909. 


New  Echinoids  —  Slocom. 


13 


The  dimensions  of  a  number  of  practically  perfect  specimens  are 
as  follows: 


Cat.  No. 

Length 

Width 

Height 

Height  of 
Periproct 

Posterior 
Angle 

Position 
of  Apex 

P  10457 

mm 

mm 

mm 

mm 

A 

24 . 2 

23.1 

IS- 

6   5    . 

75° 

Anterior 

B 

23-5 

22.8 

13  -5 

5 

1 

75° 

Anterior 

D* 

29.7 

29 . 1 

*5    ? 

6 

6 

75° 

Central 

E 

25- 

24.7 

15-3 

6 

9 

74° 

Anterior 

F 

25- 

23-5 

15  ■  7 

6 

7 

82° 

Anterior 

G 

23-9 

24  .6 

18.2 

7 

5 

85° 

Subcentral 

H 

21 . 

19.7 

15- 

8 

5 

79° 

Subcentral 

J 

20. 

20  . 

13.6 

6 

3 

85° 

Central 

Kt 

31.6 

26.4? 

23  -7? 

9 

5 

87° 

Anterior 

P  10458 

L 

26.6 

26  .4 

19  .6 

9 

8 

85° 

Central 

M 

24.9 

25-7 

17.7 

8 

2 

84° 

Central 

N 

23.8 

23-7 

*7-5 

8 

850 

Subcentral 

O 

21.7 

21.8 

15.6 

8 

5 

85° 

Subcentral 

P 

26 . 1 

24  -5 

16.3 

7 

8 

90° 

Central 

S 

24.8 

25-3 

14  -5 

6 

6 

84° 

Anterior 

T 

251 

23.6 

16  .4 

7 

5 

77° 

Anterior 

U 

24 . 2 

24.1 

16 . 2 

7 

4 

77° 

Anterior 

V 

27-3 

26.3 

15-4 

6 

7 

73° 

Subcentral 

w 

18.7 

l7  ■ 

.    10.8 

5 

1 

83° 

Central 

X 

17. 1 

16.6 

10 .  1 

4 

8 

77° 

Central 

This  table  shows  that  this  species  exhibits  great  individual  vari- 
ation in  a  number  of  characters.  Thus  the  proportion  of  length  to 
width  varies  from  wider  than  long  to  longer  than  wide ;  the  proportion 
of  height  to  length  is  variable;  the  height  of  the  periproct  varies  in 
proportion  to  the  height  of  the  test;  the  basal  line  and  the  posterior 
truncation  form  an  angle  varying  from  730  to  900  and  the  position  of 
the  apical  disc  varies  from  central  through  subcentral  to  decidedly 
anterior.  The  manner  in  which  these  variations  are  combined  is 
so  diverse,  however,  that  no  well-marked  divisions  can  be  made. 
Taking  two  extremes  of  form  such  as  B  and  L  we  find  B  longer  than 
wide,  test  low,  periproct  low,  posterior  angle  750,  apex  anterior;  in 
L  the  length  and  width  are  about  equal,  test  high,  periproct  high, 
posterior  angle  850,  apex  central.  This  combination  of  characters 
would  seem  to  be  of  specific  importance,  but  S  is  wider  than  long, 
test  high,  periproct  low,  posterior  angle  840,  apex  anterior;  F  longer 
than  wide,  test  high,  periproct  low,  posterior  angle  820,  apex  anterior; 
X  longer  than  wide,  test  low,  periproct  low,  angle  770,  apex  central. 
Hence  it  is  evident  that  these  variations  are  not  constant  but  in- 

*  Crushed  vertically, 
t  Crushed  laterally. 


14     Field  Museum  of  Natural  History  —  Geology,  Vol.  IV. 

dividual  variations.  Owing  to  this  tendency  to  variation,  the  spe- 
-cific  name  variabilis  has  been  adopted. 

Only  one  other  species  of  this  genus,  L.  tumidulus,  has  hitherto 
been  described  from  the  American  Cretaceous  and  that  species  is  so 
unlike  L.  variabilis  that  a  detailed  comparison  is  unnecessary. 

Locality:  This  species  is  from  the  Ripley  Group  and  is  quite 
abundant  both  on  the  bluffs  at  One  Mile  Run  and  near  the  southern 
•edge  of  the  village  at  Pontotoc,  Mississippi.  Two  casts  which  evi- 
dently belong  to  this  species  were  also  collected  by  the  writer  in  the 
Owl  Creek  marls  in  Tippah  County,  Mississippi. 

A  careful  examination  of  the  literature  reveals  the  fact  that  com- 
paratively little  attention  has  hitherto  been  paid  to  the  echinoids 
of  the  Ripley  Group  of  Mississippi.  The  following  are  all  the  references 
that  have  been  found  by  the  writer: 

Journal  of  the  Academy  of  Natural  Sciences  Philadelphia,  2d 
series,  Vol.  4,  p.  291.  i860.  T.  A.  Conrad  describes  Cassidulus 
■abruptus  and  C.  subquadratus  both  from  Tippah  County,  Mississippi. 

Report  of  the  Geology  and  Agriculture  of  the  State  of  Mississippi, 
i860,  p.  92.  E.  W.  Hilgard,  State  Geologist,  gives  a  list  of  fossils 
'collected  from  the  strata  of  the  Ripley  Group  in  Tippah,  Pontotoc 
and  Chickasaw  Counties,  in  which  the  following  echinoids  are 
listed : 

Hemiaster,  2  species. 

Cassidulus  subquadratus  Conrad. 

Cassidulus?  (Echinanthus?)  sp. 

Cassidulus  shape  of  Faujasia  apicalis. 

The  Echinodermata  of  the  United  States,  W.  B.  Clark,  Bull. 
U.  S.  G.  S.  Vol.  97,  1893.  The  following  echinoids  are  noted  from 
the  Ripley  Group: 

Botriopygus  alabamensis  Clark Alabama. 

Cassidulus  cequoreus  Morton Alabama. 

Cassidulus  micrococcus  Gabb Eufaula,  Alabama. 

Cassidulus  porrectus  Clark Eufaula,  Alabama. 

Cassidulus  subconicus  Clark Mississippi. 

Cassidulus  subquadratus  Conrad Holly  Springs,  Mississippi. 

Hemiaster  parastatus  Morton Alabama. 

Cassidulus  abruptus  Conrad  is  mentioned  as  a  doubtful  species. 

Geology  and  Mineral  Resources  of  Mississippi,  A.  F.  Crider.  Bull. 
U.  S.  G.  S.  Vol.  283,  1906,  p.  20.  A  list  of  the  Ripley  fauna  at  Owl 
Creek,  Tippah  County,  Mississippi,  as  collected  by  Dr.  T.  W.  Stanton 
is  given  in  which  Cassidulus  subconicus  and  C.  subquadratus  are 
mentioned. 


May,  1909.  New  Echinoids —  Slocom.  15 

The   following   list   shows   the   echinoids   and   associated   fossils 
collected  by  the  writer  on  the  Patterson  Farm,  Pontotoc,  Mississippi. 

ECHINOIDS 

Cassidulus  subquadratus  Conrad. 
Cassidulus  hemisphericus  Slocom. 
Hemiaster  lacunosus  Slocom. 

BRYOZOANS 

A  few  unidentified  specimens. 

PELECYPODS 

Anomia  argentaria  Morton. 
Cucullcea  sp. 
Exogyra  costata  Say. 
Exogyra  interrupta  Conrad. 
Gryphceostrcea  vomer  Morton 
Ostrcea  denticulifera  Conrad. 
Ostrcea  tecticosta  Gabb. 
Ostrcea,  two  unidentified  species. 
Pecten  sp. 

GASTROPODS 

Turritella  tippana  Conrad. 
Several  unidentified  natural  casts. 

CEPAHLOPODS 

Baculites. 

CRUSTACEA 

Thorax  of  a  crab,  unidentified. 

VERTEBRATES 

Shark  teeth  and  vertebrae. 

The  following  were  collected  near  One  Mile  Run  and  in  the  south- 
ern part  of  the  town  of  Pontotoc: 

ECHINOIDS 

Cassidulus  intermedins  Slocom. 
Hemiaster  parastatus  Morton. 
Hemiaster  lacutwsus  Slocom. 
Linthia  variabilis  Slocom. 


16    Field  Museum  of  Natural  History  —  Geology,  Vol.  IV. 

PELECYPODS 

Exogyra  costata  Say. 
Gryphceostrcea  vomer  Morton. 
Ostraa  denticulifera  Conrad. 

ACKNOWLEDGMENTS 

The  publications  of  P.  M.  Duncan  and  E.  Desor  have  been  freely 
drawn  upon  for  the  generic  descriptions  here  used,  but  as  they  have 
been  rearranged  and  adapted  more  or  less  they  have  not  been  treated 
as  quotations. 

President  John  GofE  of  the  Chickasaw  Female  College,  Pontotoc, 
Mississippi,  gave  the  writer  valuable  information  as  to  localities  in 
the  field  and  also  later  furnished  specimens  which  materially  aided 
in  the  preparation  of  this  paper. 


Explanation  of  Plate  I 

Cassidulus  intermedius  sp.  nov.,  page  6. 

Figs.   1-4.     Dorsal,  ventral,  posterior  and  lateral  views  of  the  type  specimen. 
Xi. 

Fig.  5.     Portion  of  the  left  posterior  ambulacral  area  at  base  of  the  petaloid 
region,  greatly  enlarged. 

Fig.  6.     Right  posterior  phyllode  with  the  adjoining  bourrelets,  greatly 
enlarged. 

Cassidulus  hemisphericus  sp.  nov.,  page    7. 

Figs.  7,  8.     Dorsal  and  lateral  views  of  the  type  specimen.       Xi. 

Fig.  9.     Portion  of  the  anterior  ambulacral  area  at  the  base  of  the  petaloid 
region,  greatly  enlarged. 


FIELD  MUSEUM  OF  NATURAL  HISTORY. 


GEOLOGY,  VOL.   IV,   PL.  I. 


Explanation  of  Plate  II 

Hemiaster  lacunosus  sp.  nov.,  page  10. 

Figs.  1-4.  Dorsal,  ventral,  posterior  and  lateral  views  of  B,  one  of  the 
type  specimens.      Xi. 

Fig.  5.  Apical  system  greatly  enlarged,  g.  genital  plates,  m.  madreporite. 
r.  radial  plates. 

Fig.  6.  Portion  of  the  anterior  petal  where  it  joins  the  apical  system, 
greatly  enlarged. 

Fig.   7.     Several  plates  of  the  right  anterior  petal,  greatly  enlarged. 

Figs.  8,  9.     Top  and  side  views  of  a  tubercle,  greatly  enlarged. 


FIELD  MUSEUM  OF  NATURAL  HISTORY. 


GEOLOGY,  VOL.   IV,  PL.  II. 


LIBKmKY 

UmVERSIIY  Oh  iLLiiMUib 

URBANA 


Explanation  of  Plate  III 

Linthia  variabilis  sp.  nov.,  page  12. 

Figs.  1-4  Dorsal,  ventral,  posterior  and  lateral  views  of  Cat.  No.  P  10457  B. 
Xi. 

Figs.  5-8.  Dorsal,  ventral,  posterior  and  lateral  views  of  Cat.  No.  P  10458  L. 
Xi. 

Fig.  9.     Apical  system,  greatly  enlarged. 

Fig.  10.     Several  plates  of  the  left  posterior  petal,  greatly  enlarged. 

Fig.   11.     Several  plates  of  the  anterior  petal,  greatly  enlarged. 


FIELD  MUSEUM  OF  NATURAL   HISTORY. 


GEOLOGY.  VOL.  IV,  PL.  III. 


10 


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